The center of Greek life was the domestic hearth which was also the sacrifical altar. Hestia, as Goddess of the Hearth, also reigned over personal security and happiness and the sacred duty of hospitality. Hestia is also credited with the invention of building houses.
In mathematics, the graph of a function f is the collection of all ordered pairs (x, f(x)). If the function input x is a scalar, the graph is a two-dimensional graph, and for a continuous function is a curve. If the function input x is an ordered pair (x1, x2) of real numbers, the graph is the collection of all ordered triples (x1, x2, f(x1, x2)), and for a continuous function is a surface.
The value $f'(a)$ of $f'(x)$ at $x = a$ is the slope of the tangent to the graph of the function $f$ at the point where $x = a.$. 2. $f'(x)$ is a function of $x:$ the slope at a point on the graph depends on the $x$-coordinate of that point.